# sha256

Calculate SHA-256 hash of a string

Agent View of the PolicyLayer registry record for `sha256`. HTML page: https://policylayer.com/tools/1595901624-crypto-mcp/sha256

## Facts

- Tool: `sha256`
- Server: Crypto_MCP (`1595901624/crypto-mcp`) — https://policylayer.com/tools/1595901624-crypto-mcp.md
- Homepage: https://github.com/1595901624/crypto-mcp
- Risk category: Read (Low risk)
- Registry record: grade A, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Allowed

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "sha256",
    "arguments": {}
  }
}
```

## Why sha256 is rated Low

SHA-256 hashing is a pure computational operation that retrieves/computes a cryptographic digest from input data without modifying, creating, deleting, or executing any external operations. This is characteristic of Read category tools. Severity is low because hash computation poses minimal risk of misuse; the tool cannot modify data, execute code, or cause financial harm.

From the tool's own definition: "Tool description states 'Calculate SHA-256 hash of a string' — a cryptographic hash function that computes a one-way digest. SHA-256 is deterministic and produces no side effects; it only reads input and returns output."

## Use case

AI agents call sha256 to retrieve information from Crypto_MCP without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

## Recommended policy (PolicyLayer)

Verdict: **Allowed**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches Crypto_MCP:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "sha256": {}
  }
}
```

## Other tools on Crypto_MCP (13)

- `des_encrypt` — Execute — https://policylayer.com/tools/1595901624-crypto-mcp/des-encrypt.md
- `aes_encrypt` — Other — https://policylayer.com/tools/1595901624-crypto-mcp/aes-encrypt.md
- `aes_decrypt` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/aes-decrypt.md
- `base64_decode` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/base64-decode.md
- `base64_encode` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/base64-encode.md
- `des_decrypt` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/des-decrypt.md
- `hex_decode` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/hex-decode.md
- `hex_encode` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/hex-encode.md
- `md5` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/md5.md
- `sha1` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/sha1.md
- `sha224` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/sha224.md
- `sha384` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/sha384.md
- `sha512` — Read — https://policylayer.com/tools/1595901624-crypto-mcp/sha512.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=1595901624-crypto-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/1595901624-crypto-mcp